1. Field
The following description relates to a magnetic sensor and a manufacturing method thereof, and to a semiconductor-based magnetic sensor for digital compass or electronic compass, a semiconductor-based magnetic sensor having Hall elements and integrated magnetic concentrators, and a manufacturing method thereof.
2. Description of Related Art
A semiconductor-based magnetic sensor detects a magnetic signal using a semiconductor device. A semiconductor-based magnetic sensor may include a combination of a plurality of Hall elements and an integrated magnetic concentrator (IMC) that performs magnetic amplification functions.
One type of magnetic sensor is a solid-state magnetic sensor that uses a semiconductor device, a Hall element, a semiconductor magnetoresistance element, and a ferromagnetic magnetoresistance element.
Magnetic sensors are used in digital compasses and electronic compasses. Geomagnetic sensors sense terrestrial magnetism and provide direction information, and are capable of being used in mobile phones, two-way radios, GPS, PDA, or navigation equipments. Digital compass is a digitized version of a magnetic compass. A magnetic compass is designed to inform its user of directions such as north, south, east and west by detecting the magnetism of the earth, and is used to determine the path of travel of ships, airplanes, and the like. A digital compass can perform the same function, and can be mounted on a portable digital device such as a smart phone. With the use of mobile applications, a digital compass can inform the user of directions such as north, south, east, and west, like a magnetic compass. Further, a digital compass that is installed on a mobile device may be used with a map application installed on the mobile device for the purpose of utilizing the direction information.
Digital compass is one type of magnetic sensors that may be manufactured using semiconductor manufacturing processes. In one type of such a compass, a plurality of Hall elements is formed on a semiconductor substrate, and integrated magnetic concentrators are formed thereon to amplify the terrestrial magnetism. The term ‘digital compass’ as used herein encompasses electronic compass, digital compass and geomagnetic sensor.
An example of an integrated magnetic concentrator (IMC) is a flat-shaped magnetic field concentrator made of a magnetic material. A magnetic sensor can be constructed with a flat-shaped magnetic field concentrator and a plurality of Hall elements arranged in a vicinity of the magnetic field concentrator to detect the direction of a three-dimensional magnetic field. In such a magnetic sensor, Hall effect occurs in the presence of a magnetic field. With the application of a predetermined voltage to the semiconductor substrate, electrons or holes move, and the direction of the electrons or holes change due to the amplified magnetic field. As a result, the path of travel is lengthened. Accordingly, resistance increases, and the Hall elements are used to detect the same. Generally, a plurality of Hall elements is arranged in the magnetic sensor to monitor the changes in resistance or the amount of electric currents.
A magnetic sensor with the above-described constitution may be capable of detecting a horizontal magnetic field with the magnetic field concentrators and may also be capable of amplifying an electric field in a region in which the Hall elements are disposed.
FIG. 1 illustrates a plan view of a magnetic sensor disclosed in U.S. Pat. No. 6,545,462, which includes a flat shaped magnetic field concentrator 3.
The above constitution has a shortcoming of increasing offset voltage due to high stress on the Hall-effect elements 2.1 to 2.6.
Recently, attempts have been made to decrease the offset voltage of magnetic sensors by reducing the stress on the thick magnetic field concentrators. The ‘offset voltage’ occurs when the Hall elements have voltage other than zero in the absence of the magnetic field.
Higher offset voltage leads into higher possibility of malfunction. High offset voltage causes minute changes in the actual voltage of the Hall elements in the presence of a magnetic field, and thus deteriorates the sensitivity of the magnetic sensor.
By lowering the signal-to-noise value, high offset voltage causes shortcomings such as difficulty of detecting minute changes in a magnetic field. Accordingly, the reduction of the offset voltage and the improvement of sensitivity are desirable.